Why IRC Servers like Ident

The reasons are not historical at all. When IRC turned into lamer's favorite past-time ident became a must. It prevented multiple logins from a single user as the usual goal of such user was to flood (aka DoS attack) another user. Since then most irc clients have a built in flood protection, and the old floods usually dont work. However almost all irc servers require that your box responds to an ident request.

PS: I'm reading this 5 minutes later...and it's a friggin historical reason..im going to bed